1. Field of the Invention
The present invention relates to a lens-fitted photographic film unit with a flash device, and more particularly to a lens-fitted photographic film unit in which the flash device emits a flash for each exposure.
2. The Known Prior Art
lens-fitted photographic film units (hereinafter simply referred to as film units) are widely known and sold at low prices. As disclosed in U.S. Pat. No. 4,884,087, such a film unit consists of a film housing having a preloaded photographic film and a photograph-taking mechanism, and a decorative outer casing in which the film housing is encased. Furthermore, the film unit is enclosed in a wrapping having a hang hole by which the film unit is hung on a hanger for display at a shop.
After purchasing the film unit and removing its wrapping by tearing, photographs can be taken with the film housing encased in the outer casing. When available frames of the photographic film are entirely exposed, the film unit in its entirety is forwarded to a photo-finishing agency for development.
There are also known film units having a flash device including a flash circuit, a flash button, a dry cell battery and the like. When a flash photograph is desired, a flash button is depressed to charge main and trigger capacitors in the flash circuit. The flash button is kept depressed until the completion of the charging can be ascertained by lighting of a pilot lamp. Then, the flash button is released and upon depression of a shutter release button, a trigger switch for generating a trigger signal is turned on to cause the trigger capacitor to be discharged, when the shutter blade is fully open. Accordingly, when high voltage is applied to a trigger electrode for a flash discharge tube by the trigger circuit, the current from the main capacitor flows into the flash discharge tube to emit a flash. The depression and release of the flash button can be repeated as needed.
However, this operation of depressing and releasing the flash button is troublesome for users. Therefore, users are liable to forget to carry out this operation or to discontinue it before the pilot lamp is lit, resulting in under-exposed frames. It would be possible to always turn on a booster circuit of the flash device, taking advantage of the single-use characteristics of film units. But it is not appropriate to do so from the moment of shipment since the lifetime of the battery is limited.